Up to now, sulphur containing fuels have been prohibited from use as energy sources because, as everyone knows, when sulphur burns, oxides of sulphur are formed which, when combined with water, form acids of sulphur. However, even non-sulphur fuels, when burned, inherently form oxides of nitrogen, which can also be dangerous to health, if in sufficient concentration. The production of nitrogen oxide cannot be prevented because of the high burning temperatures as the production of nitrogen oxides rises with the combustion temperature. These oxides, when in the atmosphere, often combine with water in the vapor state to form nitric acids. In addition, when coal is used as a fuel, relatively large quantities of metal oxides are formed because coal contains traces of many metals. These metal oxides, being solids, are termed fly ash. The main objection to fly ash is that it dirties everything it settles upon and it does get into one's lungs.
Fly ash can be successfully removed by filtering flue gases through what is commonly termed "bag houses." However, the objectionable noxious oxides, being in the gas state, cannot be readily filtered. The prior art teaches spraying the flue gases directly with water to cause the objectionable gases to become dissolved therein and be washed away. This process is costly because, for one thing, the flue gases are cooled to the point that the remaining flue gases, primarily carbon dioxide, cannot rise into the atmosphere to form a draft to promote combustion. In addition, besides needing energy to provide a draft, energy is required to form the water sprays, which energy cannot be recovered.